1. Technical Field
The present invention relates to phase control of a signal and, more particularly, to methods, devices and apparatuses for conforming a signal to a target phase trajectory.
2. Description of the Related Art
Precise frequency ramping is often an important aspect of frequency synthesis and clocking applications. One specific example of such applications is a frequency modulated continuous-wave (FMCW) radar system, which uses linear frequency ramps for clock synthesis. Precision is also important in dynamic frequency scaling (DFS) applications for controlling microprocessor or application-specific integrated circuit (ASIC) clock signals.
To implement frequency ramping, both open-loop and closed loop systems can be used. For example, frequency ramping can be achieved in an open loop system by sweeping a voltage controlled oscillator (VCO) control voltage to generate an output frequency profile. Off-line calibration can be employed to support this system. Frequency ramping in open loop systems can alternatively be implemented by applying filters that modulate the natural dynamics of a phase-locked loop (PLL). In closed loop systems, an analog PLL can be used to track an input reference with a time-varying frequency. Alternatively, closed-loop systems can institute frequency ramping by adjusting a feedback divider value in a fractional-N synthesizer. Precise frequency ramping can be achieved in a variety of ways with varying degrees of success.